Can KDM run multiple instances of itself?

Duncan 1i5t5.duncan at
Wed Mar 2 08:31:50 GMT 2011

Allistar posted on Wed, 02 Mar 2011 13:07:13 +1300 as excerpted:

> HB wrote:
>> Hi,
>> I want to upgrade my out-dated OS to a newer release, but it uses GDM
>> which has been "improved" into uselessnes.  If I were to upgrade and
>> replace GDM with KDM, would I be able to run multiple instances of KDM?
>> I need to have multiple log-in screens (3 by default) running.  Also,
>> is it possible to configure so that it loads on a specific VT?
>> I want my new system to be configured the same as now, which is thus:
>> VT 1-4 getty VT 5-7 Xorg/KDM VT 8-9 available VT 10-12 logs
>> Is this possible with current version of KDM?
> It can with Kde 3.5, but not with KDE4 if you're also running Plasma
> (which KDE4 does by default). Plasma cannot be run multiple times which
> effectively broke the multi-screen capability of KDE. I run a triple
> head setup and the only way to get this to work in a 3D accelerated
> fashion is to run a different VM (e16) on the 3rd display.

OK, I don't use a *dm (? desktop manager, the graphical login client) at 
all, preferring to login at the text prompt, and don't even have kdm 
installed (thus resulting in a dialog warning saying will not lock session 
as unlocking would be impossible, no greeter applet found, when I choose 
the lock desktop option from the plasma-desktop menu... the greeter applet 
is apparently the kdm login dialog), so obviously I don't know from 
personal experience here, but...

Forgive me for saying so but while your statement may indeed be true of a 
single X instance in zaphod mode (multiple separate WM sessions on 
separate X screens of the same X instance), your post makes little sense 
in the context of this thread, multiple separate X instances, each in its 
own VT, with (if configured so) its own *dm.

Either that or what /I/ understand of the topic may be incorrect, which is 
certainly possible, and by posting, hopefully my understanding will be 
corrected if necessary.

Why would plasma's inability to run multiple times interfere with kdm, 
which is kde's *dm (X-based graphical login utility), and its ability (or 
not) to run on multiple login screens (on multiple X-controlled VTs), 
given that kdm by definition runs before the user login session starts, 
and thus before plasma (at least on that VT)?

Meanwhile, triple-heads managed by the same X instance, as you appear to 
be talking about, really don't have a lot to do with multiple entirely 
different X sessions, each run on its own VT (normally sharing the same 
hardware keyboard(s)/mice/monitor(s), thus, VT, "virtual terminal" as 
opposed to simply terminal or physical terminal).  Based on previous 
threads, multi-head "Zaphod mode", where each gets its own *dm on the same 
X instance, does indeed not work with kde4 (or at least plasma, as you 
indicate) at present, but IDR seeing any previous questions about multiple 
X instances, each in its own VT.  It is indeed /quite/ possible that 
plasma won't work with that either, at least logged in as the same user, 
but it may be possible to login as different users on the different X 
sessions, since at least in theory, the different plasma sessions should 
then run /as/ the different users and one user's apps aren't normally 
supposed to be able to interfere with another's, especially at the CLI or 
when they're in entirely different X instances on separate VTs.

So while your version of the question (multiple plasmas running on 
separate X-screens on the same X-instance) is to my knowledge indeed 
settled in the negative, this is, again to my knowledge, the first time 
the OP's version of the question (involving entirely separate X instances, 
each on its own VT, and kdm, not necessarily a kde logged-in session and 
thus not necessarily the plasma-desktop at all) has been asked.  And it 
has (again to my knowledge) yet to be answered.

Now, it /is/ possible that kdm now uses plasmoids in its greeter/login (I 
seem to remember discussion of this in some kde dev blog, but again, no 
personal kdm experience, so...), potentially making the answer the same 
for it as for plasma in general, but in that case the "if you're also 
running plasma" qualification is invalid, since kdm would then be a 
special case of the plasma general case and given the question is /about/ 
kdm, one would then be running plasma by definition.  (However, this bit 
fails to stand up since the *dm is normally respawned as soon as it 
terminates, and if it's another plasma, the plasma-desktop session the 
user had chosen would then be a second plasma instance, which you say 
can't work, yet this does, so it's therefore safe to conclude that kdm is 
NOT a plasma instance at least to this degree, thus invalidating the whole 
possibility considered by this paragraph.)

And FWIW, from what I've read, e16 normally refers to version 16 of the 
enlightenment window manager (WM), not some sort of virtual machine (VM).

So as I said above, one or the other (maybe both?) of us has an incorrect 
understanding.  If it's me, please do try to point out the error so it can 
be corrected, as I tried to do with what I /think/ is your incorrect 
understanding, above.

Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

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